Carpenter v. United States, 138 S. Ct. 2206 (2018)
Carpenter v. United States reshaped Fourth Amendment doctrine for the digital age.
Does the government's warrantless acquisition of historical cell-site location information (CSLI) from a wireless carrier under 18 U.S.C. § 2703(d) constitute a Fourth Amendment search that generally requires a warrant supported by probable cause?
An individual maintains a legitimate expectation of privacy in the record of his physical movements as captured through historical cell-site location information. The government's acquisition of such CSLI from a third-party carrier is a search under the Fourth Amendment, and law enforcement must generally obtain a warrant supported by probable cause to access it. The traditional third-party doctrine does not automatically apply to CSLI because it is not truly voluntarily conveyed and is deeply revealing. This holding is narrow and does not address real-time CSLI, so-called "tower dumps," other business records beyond CSLI, or national security considerations; established exceptions (e.g., exigent circumstances) remain available.
Yes. Obtaining historical CSLI from a wireless carrier is a Fourth Amendment search, and the government must generally secure a warrant supported by probable cause before acquiring such records. The SCA's § 2703(d) orders, which require only reasonable grounds, are insufficient.
Carpenter narrows the third-party doctrine and marks a major shift in Fourth Amendment law for digital data. It recognizes a reasonable expectation of privacy in location information despite its possession by a service provider, signaling that the mere involvement of a third party no longer categorically eliminates privacy claims where the data are pervasive, automatically generated, and deeply revealing. For law students, Carpenter is essential to understanding how courts adapt Katz to modern technologies and how factors like pervasiveness, voluntariness, and the granularity of data influence the privacy analysis. It also guides practitioners: when investigating suspects, officers should generally obtain a probable-cause warrant for historical CSLI and analogous datasets, and defense counsel should scrutinize government access to location-rich or behavior-revealing digital records.